Effects of the surface modification of polyurethane substrates on genotoxicity and blood activation processes.

The aim of this study was to determine the mutagenic and thrombogenic potential of a material composed of a thin coating deposited on a polymeric substrate. In this work, a surface was modified in a manner that would mimic the function of cellular niches. Finally, the surfaces should actively capture and differentiate progenitor cells from the blood stream. Thin films with 10 to 500nm thicknesses were deposited by unbalanced, pulsed DC magnetron sputtering on smooth polyurethane. Such high energy conditions led to a stiffening of the polymer surface layers by pseudodiffusion during the initial stages of film growth. Both the high intrinsic film stress due to high energy film growth and the huge difference in the elastic properties of the films and polymer substrates resulted in hierarchical and self-adapting nanowrinkling. Surface modifications of synthetic materials for future use in regeneration of the circulatory system must be tested in terms of their thrombogenicity and mutagenicity. Point mutations in many cases can lead to many serious haematologic complications. Genotoxicity was determined by testing for reverse histidine mutations in selected strains of Salmonella typhimurium. The analysis was performed in the presence and absence of metabolic activation system S9 containing liver microsomal fraction of rats. Based on these results, no mutagenicity of the tested material was observed. The interaction of blood and the material under dynamic conditions was described. Blood from above the analysed surface was collected after the test, and the quality of the blood was assessed along with the type of cellular response to the surface. In the obtained results of the coagulation processes, it was found that the tested material reduced the process of platelet activation under hydrodynamic conditions in comparison to the control material, polyurethane.